This invention relates to a process for reducing the formation of carbonyl halide in bromine chloride. The process may be employed during the production and/or storage of bromine chloride.
Bromine chloride is well known as a bromination agent and as a water treatment chemical. Moore, et al. U.S. Pat. No. 3,845,146, discloses the bromination of benzene, lower alkyl benzene, phenol, biphenyl and diphenyl oxide with bromine chloride in the presence of iron or a Friedel-Crafts catalyst. The resultant brominated products are useful as flame retardants. Barda, et al., U.S. Pat. No. 4,352,909, discloses that polystyrene can be nuclear brominated with bromine chloride in the presence of a chlorinated hydrocarbon solvent and a catalytic amount of a Lewis acid catalyst. The use of bromine chloride as a water treatment chemical is illustrated in U.S. Pat. No. 2,662,885.
While bromine chloride is safely used in commerce, its high reactivity argues well for care in its production, use and storage. Normally, bromine chloride is kept under a pad of a commercially available inert gas, e.g. nitrogen, argon, etc. While the use of such a pad prevents most undesirable reactions between the bromine chloride and its environs, it has been now been discovered that some bromine chloride will still contain, as an impurity, phosgene or carbonyl halide which cannot be attributable to the bromine chloride's method of manufacture. Thus, despite the use of prior art pads, the bromine chloride is still entering into an undesirable impurity producing reaction.
The presence of an impurity such as phosgene in the bromine chloride can severely limit the use of such bromine chloride in the manufacture of brominated organic compounds if the phosgene interferes with the manufacturing process. For example, in the bromination of aromatics, a carbonyl halide poisonable catalyst, such as a Friedel-Crafts catalyst, is used. Thus, the use of a bromine chloride which contains a carbonyl halide, such as phosgene, would result in catalyst poisoning and a resultant degradation of process efficiency. Due to the presence of carbonyl halide in most commercially available bromine chloride, many of today's catalyzed bromination reactions suffer from catalytic poisoning.
It is therefore an object of this invention to provide bromine chloride which is substantially free of carbonyl halide impurities.
It is another object of this invention to provide an improved process for the bromination of a compound with bromine chloride in the presence of a carbonyl halide poisonable catalyst.